There are a variety of instances where it is desired to separate a fluid from a mixture of fluids. For example, in many machining operations, an aqueous coolant is sprayed or flowed at the location where a cutting tool engages the workpiece for lubrication and cooling purposes. The coolant is then collected in a tank and recycled for continuous use for as long as possible. Aqueous coolants of this type are fairly expensive. Consequently, it is advantageous to maintain such coolants in a usable condition for as long as possible. Typical machining operations also employ lubricating oils for lubricating moving parts. Eventually, the lubricating oils drip or flow into the tank where the aqueous coolant is being collected. In the tank, the lubricating oils float upon the surface of the coolant because they are of a lighter weight and lower density than the coolant. These lubricating oils, typically referred to as “tramp oil,” eventually contribute to bacterial growth within the tank holding the aqueous coolant, resulting in a foul odor and reducing the useful life of the aqueous coolant. Moreover, due to environmental considerations, the oil-contaminated aqueous coolant must be treated as a hazardous waste and its disposal represents an environmental and economic concern.
A number of separating, or skimming, devices have been developed over the years to remove tramp oil from the surface of an aqueous coolant held in a tank associated with a machining operation. One type of such device is a disk skimmer that includes a disk which extends into contact with the tramp oil that has collected on top of the aqueous coolant. Rotation of the disk adjacent the surface of the fluids in the tank results in removal of the tramp oil from the tank. The tramp oil is scraped from the disk by a blade, collected and removed. Belt skimmers also are used. Such skimmers employ an endless belt that removes the tramp oil from the surface of the aqueous coolant. As with the disk skimmers, the tramp oil is scraped from the belt, collected and removed.
Tube skimmers also are available for removing tramp oil from the surface of an aqueous coolant. A tube skimmer can be mounted to the side of the tank containing the tramp oil and coolant and involves running an endless, flexible, small diameter tube into the tramp oil at the surface of the coolant. The tube collects the tramp oil on its outer surface and brings the tramp oil to a scraper where the tramp oil is removed and deposited in a suitable container for disposal. However, conventional tube skimmers frequently suffer binding and jamming problems with the tube.